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MELBOURNE, AUSTRALIA — Japan's Kirin Brewery Co. Ltd. of Yokohama has developed new carbon-coating technology for PET bottles that extends their shelf life and allows multiple washings and refillings.

Although PET is becoming an increasingly popular liquid packaging material because of its light weight and durability, its inferior gas- and flavor-barrier properties, compared to glass, limit shelf life and restrict reuse, said Eihaku Shimamura, a Kirin packaging engineer. He spoke at the International Association of Packaging Research Institutes world conference, held March 24-27 in Melbourne.

Shimamura said tests showed that by applying the hydrocarbon film to the inside wall of a PET bottle, its barrier property for oxygen is more than 50 times better than conventional PET and its barrier property for carbon dioxide as much as 100 times better.

The coated bottles also can withstand as many as 30 washings at 158 F.

Although Kirin Brewery now packages its beer in glass, it has been investigating alternatives for several years, he said. The brewery developed and tested the hydrocarbon film in conjunction with a university in Kyushu, Japan.

The brewery has no immediate plans to commercialize the technology, because it needs to do more testing on whether Japanese consumers would accept beer packaged in PET, he said.

``We have no product yet. We have completed scientific tests, but need to do more practical research on consumers, markets and recycling,'' Shimamura said.

Last year, Australia's Carlton & United Breweries Ltd. of Melbourne launched what it claimed was the world's first PET beer bottle. It has a shelf life of only six weeks compared to beer bottled in glass, which has no specific date it must be used by.

Shimamura said the carbon-coated film could be applied to bottles used for beer and other oxygen and carbon-dioxide sensitive liquids, such as soft drinks. If the technology is approved for public use, the company could license it commercially, he said.

Meanwhile, Danish researchers have developed a standardized system for measuring carbon dioxide loss from filled PET bottles that they say will make the containers more viable for products like beer.

Poul Jensen, head of materials and testing at the Danish Packaging & Transportation Institute in Copenhagen, Denmark, said DPTI has developed a measuring system — based on an infrared carbon dioxide sensor and testing chamber — that can determine carbon dioxide loss over time, forming the basis for more accurate shelf-life estimations. Not yet commercially available, the testing equipment will sell for A$10,000 and A$15,000 (US$7,800 and US$11,700), Jensen said.